Foldable ladders are well known and have been in use for many years. An extremely old and very common type of foldable ladder is a so-called rope ladder. These usually comprise a series of elongated rigid steps maintained approximately parallel to each other by two ropes, one secured to each end of the steps. The rope permits rolling the ladders into a cylindrical bundle.
Several types of storable, foldable fire escape devices are known. Such devices are described in U.S. Pat. No. 2,388,678 of Dahlander and U.S. Pat. No. 4,127,184 to Strohmeyer.
U.S. Pat. No. 4,231,449 to Laurita discloses a foldable ladder having inwardly foldable links. However, the construction of the links would make the ladder heavy and costly to produce.
In order for an escape ladder to be commercially appealing and capable of use in an emergency, it must not be complicated but must be light weight. The construction must be simple and capable of use by women and children. The cost of the ladder should be such as to make it available to lower income groups.